CONTRIBUTIONS TO BOTANY. 
43 
the embryo of Viscum cannot be owing to the cohesion of several 
embryos. It appears to me that many of the changes that 
really take place in such cases have not yet been observed, and 
that we have still much to learn concerning the true nature of 
such developments : this is a subject of deep interest, worthy of 
the most attentive examination. I have mentioned that in the 
Olucacece, as well as the Santalacece, although the cionosperm 
sometimes exceeds the limits of the ovules, the free apices of the 
three ovular bodies are more frequently seen to extend above 
the top of the column. M. Decaisne describes the ovules in 
Viscum album to be sevei’al and erect, that one of these becomes 
fertile, while the two others are abortive and appear like filaments 
at its base. It is probable that the cionosperm is here very short, 
and that the free apices of the ovules have been mistaken for the 
ovules themselves; it may be also that the free apices of the 
probably yet unimpregnated ovules, distinguishable in the ova- 
rium of the Olacacece, Santalacece, &c., may be nothing more than 
the exserted poi’tions of the embryonary sacs, so ably described 
by Mr. Griffith : these are points very difficult of determination 
in dried plants especially, where the parts are so extremely minute 
and delicate. In Opilia, and again in Champereia, the three 
suspended ovules, at the period of the fall of the flower, appear 
closely aggregated upon their columnar support, and from their 
extreme minuteness, they are easily mistaken for a single erect, 
stipitate ovule ; but I have found, by alternately moistening and 
allowing them to dry, that air intervenes between the delicate 
membranes, and renders them clearly distinct. I have already 
alluded to the fact, but as yet we know nothing of the cause, of 
the non-production in all the Cionospermce, as well as in Viscum, 
of the usual coverings that in ordinary cases are generated over 
the pristine ovule. We must not lose sight of the important 
circumstance, observed by M. Decaisne, that in Viscum album 
the embryo is not developed till a long period after the fall of 
the anthers*, nor of those of Mr. Griffith f, equally showing, 
that both in the Indian species of Viscum and Loranthus, the 
ovulum is a formation, subsequent to the act of impregnation ; 
“ a remarkable and unparalleled fact, that tends to increase the 
difficulty of understanding, or even conjecturing, the nature of 
the first steps in the formation of an embryo.^’ These con- 
siderations become analogieally of importance in leading us to 
the discovery of the real history of the Olacacece. Something 
in relation to this subject might be learned, if we could better 
understand the origin and development of the embryo under 
* Sur le (leveloppement du Pollen du Guy, &c., Mem. Acad. Roy. 
Bruxelles, vol. xii. 
t Linn. Trans, vol. xviii. p. 77- 
G 2 
